A former Boeing production manager said that before the two crashes of the 737 MAX jet that both the company and federal regulators ignored his warnings that fatigued workers at a MAX assembly plant could make mistakes endangering the lives of passengers.

NBC News and The New York Times reported on Tuesday that Edward Pierson told them about his concerns after learning some production workers at Boeing's plant near Seattle worked 50 to 60 hours a week -- and some worked for as much as two months without time off as Boeing increased production of its best-selling plane to 52 a month from 47 to keep pace with rival Airbus.

Pierson said the push to increase production of the 737 MAX created a "factory in chaos'.

Pierson is scheduled to testify Wednesday before the House Transportation Committee in Washington investigating the crashes of the Lion Air flight in Indonesia and the Ethiopian Airlines flight in Africa.

Steve Dickson, head of the US Federal Aviation Administration (FAA), is also scheduled to testify.

"The suggestion by Mr. Pierson of a link between his concerns and the recent MAX accidents is completely unfounded," Boeing said in a statement.

"Mr. Pierson raises issues about the production of the 737 MAX, yet none of the authorities investigating these accidents have found that production conditions in the 737 factory contributed in any way to the accidents. The suggestion of such a linkage is inconsistent with the facts that have been reported."

Pierson said in interviews with NBC and the Times that long hours on the production line resulted in damaged parts and tools improperly left in MAX planes. He said that he recommended a temporary halt to production to improve quality control and to give workers a rest, but that Boeing didn't follow his suggestion.

On June 9, 2018, Pierson said in an email to Scott Campbell, general manager of the 737 MAX program: "Frankly right now all my internal warning bells are going off. And for the first time in my life, I'm sorry to say that I'm hesitant about putting my family on a Boeing airplane," NBC and the Times reported.

In October 2018 and March 2019, two MAX aircraft crashed, killing all 346 passengers and crew onboard. The planes involved in the fatal crashes in Indonesia and Ethiopia were built at the Renton, Washington, plant, but investigators have focused on the software in the aircraft's automated anti-stall device -- not a manufacturing hardware fault -- as the cause of both crashes. Pierson didn't raise concerns about the anti-stall system.

Boeing said it closely monitors production, and all planes "are subject to rigorous inspection before they are certified, delivered and enter into service".

Pierson said he took his concerns to the National Transportation Safety Board (NTSB), but the agency investigates crashes and, after reviewing his concerns, said it lacked jurisdiction to proceed on a workplace issue. The NTSB suggested the Inspector General was the best office to review the claims, according to the news reports.

In a statement to NBC News, the FAA said it takes all whistle-blower reports seriously and that it had "interacted on several occasions" with Pierson and his attorneys.

Pierson, who retired in August 2018 after a career in the Navy, declined to say if he would seek whistleblower protection or if he planned to file a federal whistleblower case. But he has hired Eric Havian, a well-known lawyer in the field, and Pierson "could stand to gain monetarily if he pursued such a case', the Times reported.

All MAX aircraft have been grounded since March 2019.

Investigators believe the plane's automated anti-stall device, called the Maneuvering Characteristics Augmentation System (MCAS), erroneously pointed the nose of the planes down to avoid a midair stall and into a fatal plunge. Boeing has updated the software and submitted it to the FAA for review, but the regulatory agency has not yet approved it.

When developing the MAX, Boeing knew it had to act quickly to preserve market share. It therefore abandoned plans for a new plane because design, testing and certification could take as much as 10 years, so Boeing decided to update an existing model, the 737 NG.

The new, fuel-efficient engines on the MAX are larger and positioned farther forward on the wing and closer to the fuselage than those on the NG. The extra weight changed the plane's handling characteristics, and it performed differently than previous versions. To compensate, Boeing developed the MCAS.

Critics say that Boeing didn't adequately inform pilots of the new system or tell them how to turn it off in an emergency.

Boeing hoped to return the planes to service this month, but it now appears the MAX won't be recertified until next year, perhaps March at the earliest. US regulators said stored planes will be individually inspected before returning to service.

Regulators in different countries may set different training standards for pilots, further delaying the plane's return.